Ireland's Nicolas Roche (Team Sky) has outsprinted Spain's Haimar Zubeldia (Trek Factory) to claim victory in stage 18 of La Vuelta a Espana.

Roche now lies 26th in the overall standings with the Netherlands' Tom Dumoulin retaining the red jersey.

Dumoulin comfortably held off a string of attacks from closest rival Fabio Aru to maintain his slender lead in the GC. Aru (Astana) tried at least five times to drop Dumoulin (Giant-Alpecin) on the hilly 204km ride between Roa and Riaza but the 24-year-old from Maastricht stayed glued to the Italian's wheel before they crossed the line together.
              
Roche (Team Sky) won the stage by outsprinting Spaniard Haimar Zubeldia (Trek), with Jose Goncalves of Portugal (Caja Rural) third and home rider Alejandro Valverde (Movistar) fourth.
              
Dumoulin, who claimed the leader's red jersey with a scorching time trial on Wednesday, is three seconds ahead of second-placed Aru with three stages remaining including Sunday's ceremonial finish into Madrid.      

Roche was delighted hopes of a stage victory "finally worked out" as he sealed the triumph in Riaza.

He told Eurosport: "There was a rider 20 seconds behind and when we saw that I just said 'let's just ride to the finish and we'll do a mano a mano sprint'.

It was actually really good and we co-operated well since the 15km to go sign. I think that was our only chance.

"Coming into the sprint I wanted to lead it out. Haimar is someone who has got a lot of experience and I've lost a few sprints against him in the past, in (Clasica) San Sebastian for example.

"I didn't want to have a slow-start sprint, I wanted to have a really high speed one.

"I thought I'd try and manage my own pace. I smiled because I was happy that it worked. I thought 'yes, for once I didn't mess up'.

"I've had a few second and third places and I've always lacked that little small bit at the finish. Today it finally worked out."

Dumoulin told reporters: "There are hard days coming up but we've survived the first one and it was a good day.
              
"Aru tried very hard but I actually was never in trouble and after his first attack I knew I would keep the red jersey."
              
Joaquim Rodriguez of Spain (Katusha) is more than a minute behind in third and Poland's Rafal Majka (Tinkoff-Saxo) nearly two and a half minutes adrift in fourth.
              
The first Dutchman since Joop Zoetemelk at the 1980 Tour de France to lead a grand tour in the final week, Dumoulin is in a strong position to secure a debut triumph in one of cycling's premier races.
              
Aru, however, who was second in this year's Giro d'Italia, will look to make his climbing ability count particularly on Saturday's mountainous 20th stage from San Lorenzo de El Escorial to Cercedilla.